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Re: Hotspot in Accelerate Framework

On 3 Jan 2005, at 06:22, Steve Peters wrote:

On Jan 2, 2005, at 12:04 PM, email@hidden wrote:

Interesting ... ATL_srot_xp0yp0aXbX is the ATLAS BLAS fallback case for non-unit stride along X or Y. This case is *not* aggressively optimized because it almost certain to be *memory* bound. Shark shows nearly 25% of the total run time consumed by loading operands from memory in this routine. How are you calling sgells_? (I'm trying to understand where the non-unit strides are introduced.)

I wondered if it was something like that.

I've submitted a bug at Ian O's suggestion (3936624).

The call which causes this is as follows

sgelss_(&nRows, &nColumns, &nRHS,
(float *)[equationMatrixRedA bytes], &nRows,
(float *)[equationMatrixRedb bytes], &nRows,
(float *)[sArray bytes], &rCond,
&rank,
(float *)[workMatrix bytes], &workSize,
&info);

where
nRows ~= 1800
nColumns ~= 450
nRHS = 1
rCond = -1

equationMatrixRedA is a NSData nRows * nColums * sizeof(float) in size.
equationMatrixRedB is a NSData nRows * nRHS * sizeof(float) in size.
sArray is a NSData MIN(nRows,nColumns) * sizeof(float) in size.
workMatrix is a NSData workSize in size.

workSize is obtained by doing a query call to sgells_ (i.e. worksize set to -1 all other parameters the same), just previous to the main call.

The call stack is given below. There only appears to be the one call path.

libBLAS.dylib ATL_srot_xp0yp0aXbX
libLAPACK.dylib f2c_srot
libLAPACK.dylib SBDSQR
libLAPACK.dylib sgelss_

Paul
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 >Re: Hotspot in Accelerate Framework (From: Steve Peters <email@hidden>)



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